Climate change: the Bigfoot connection

In 5 seconds Using data from sightings of the mythical creature, UdeM biologist Timothée Poisot adapts a machine-learning method to map the uncertainty of biodiversity scenarios.
A photo montage combining a misty forest with a photo of a Japanese snow monkey, created to give the impression that Bigfoot is wandering through the forest.

To effectively protect biodiversity in an era of climate change, ecologists first have to know where animal and plant species are located and then be able to predict what habitats will be available to them in the future.

To help them in these tasks, the scientists use species distribution models that identify species’ habitats from observational data and climate scenarios.

Trouble is, these models are often severely limited.

They often aren't good at accounting for uncertainty: if the species is not sufficiently well-described, if the relevant climatic conditions are poorly understood, or if the model is simply not very accurate, the models tend to be inaccurate.

 So when they're used to guide public policy or assess the effectiveness of decision-making, it becomes crucial to say when their predictions might be flawed.

This is the methodological problem addressed by Timothée Poisot, a professor in Université de Montréal Department of Biological Sciences. 

In a study published in Advances in Ecological Research, he adapts a well-established method in machine learning that has not yet been used in biodiversity research – conformal prediction — to propose a new approach to mapping the uncertainty of biodiversity scenarios.

How? By using data from sightings of a rather unusual (and fanciful) species: Bigfoot (also known as Sasquatch), the large, hairy, mythical creature that's said to inhabit forests in North America, particularly in the Pacific Northwest.

"When developing a new method, we often use simulated data, and that always frustrates me because the simulations are too clean," Poisot explained. 

"But the community that believes in the existence of Bigfoot has a database of all the sightings, and it’s a dataset that’s perfectly suited to this exercise. So by demonstrating how the method works on realistic data, we’re taking a step back from the biology itself."

More emphasis on choices

This new approach places greater emphasis on the choices made by users of the scenarios.

"We can choose the level of uncertainty we are willing to work with; if we want to detect an invasive species at an early stage, or take very costly action to protect a rare species, the risks we are willing to tolerate are different," said Poisot.

"We can also map uncertainty into the future."

In trying to predict how species respond to climate change, scientists make a central assumption: their confidence in their models should decrease as the climate becomes increasingly different from historical conditions. 

But by projecting uncertainty on the the Bigfoot model, it would appear that this assumption is not always borne out, said Poisot.

“In our study of the Bigfoot crowd, the areas where the climate was set to change the most were not those where model uncertainty increased. This suggests that our models can generalize to changing climates, but that they retain some of their uncertainty.”

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